Paper making



Patented Mar. 1, 1932 UNITED STATES ERNEST LION'NE, OI SWLIPSCOT'I', IASSACHUSETTS PAPER MAKING No Drawing.

This invention relates to paper making.

A paper is often required which has characteristics not natural, at least in a marked degree, to the paper as, for instance, a high degree of mechanical strength, high electrical resistance, insensibility to liquids, acids, al kalis and the like.

Paper has been treated to modify its characteristics, as is the case of parc mentized paper,-but the time and expense involved in making such paper is highly objectionable.

Paper has been made'with a sizing, as a rosin or a glue sizing, but the amount of sizing that can be put in the paper is too small to influence the characteristics of the paper sufficiently for my purpose.

One of the objects of the presentinvention is a paper which contains a material, and particularly a resin, that imparts'its characteris tics to the paper in accordance with the amount of the material in the paper; and to a process for making such paper.

Another object of the invention is the prO- vision of a paper containing such a large amount of a material, as a resin, that the paper is characterized largely by the characteristics of the material in the paper; and to a process for making such paper.

Another object of the invention is theprovision of a paper containing a water-insoluble jelly that is present in the finished paper as a dry coherent solid, which substance has been incorporated with the paper making fibres prior to the felting of the fibres.

A further object of the invention is the provision of a paper containing a carbamide, as a urea or a thiourea forma dehyde resin; and a process for making such paper.

In one of its aspects, my invention consists of a paper sheet that is made by mixing a water-insoluble colloidal body, preferabl in a jelly form, with the paper making fi res prior to the laying of the sheet, thus to impart to the sheet much of the characteristics of the material. For instance, a glue or casein which has been rendered insoluble by a well known tanning agent and is in a jelly form can be incorporated in the paper sheet in the manner presently to be explained.

While a paper sheet having such a material rosin, as a rosinate of soda.

Application flied September 28, 1928. Serial No. 809,119.

incorporated therewith is useful for certain purposes, it has properties, such as that of absorbing moisture and swelling, which limit the usefulness of the paper for my specific purposes. I specifically desire a paper which to as great a degree as is possible is non-hygroscopic and issubstantially insensible to moisture and to many acids and alkalis and has good electrical resistance and mechanical strength. To prepare such a paper, I incorporate with the paper making fibres a colloidal material in a jelly form which has such characteristics and can impart them to the finished Ipaper. The material best suited for my speci 'c purpose is asynthetic resin resulting from the reaction of a urea and formaldehyde and my process will be described specifically in connection with such resin.

Many attempts have been made in the past to obtain a resin-containing paper by beating a resin with the mixture of paper making material such as wood pulp, rag stock, and the like in the paper beater, whereby to get a good mixture of the resin with the paper making fibres prior to forming the paper sheet, so that the resin will remain with the fibres when the paper is made. When the resin can be saponified, its mixture with the paper fibres in the paper heater is comparatively simple. The resin is usually furnished to the beater as a soap, and in the case of The rosin is afterwards precipitated onto the paper making fibres by alum or some other suitable agent.

If the resin is not saponifiable but is easilyput into the form of an emulsion, it can be added to the paper making fibres in the beater and produce a satisfactory paper sheet. Such is the case for example with copal resin or some hydrocarbons similar to resins in their behavior, such as asphaltum, gilsonite, paraflin and the like.

If the resin, either natural or synthetic, can not be either saponified or emulsified but is soluble in suitable solvent, the resin can be dissolved in a solvent which is miscible in water. The phenol synthetic resins are susceptible to such treatment as such resins are insoluble in water but are soluble in alcohol or acetone and the solutions thereof can be mixed with water. This method of adding the resin to the paper heater is possible, but is highly objectionable by reason of the large expense for the solvent which must be Wasted and also because almost all of the resin solution will flow through the paper making wire and be lost. The best manner in which such resins can be added to the paper beater is to grind the resin as finely as possible. The mixture ofthe resin thus prepared in the beater will not be very satisfactory, however, because of the comparatively large slze of the resin particles, which prevent their being disseminated uniformly throughout the paper sheet and also because they will flow into the interstices of the paper making wire and clog it.

I have discovered that a particular form of urea formaldehyde synthetic resin can be mixed with the paper making fibres in the beater and the resultant mixture made into a paper sheet which will have novel characteristics without the necessity either for saponifying the resin or for dissolving it in a solvent or for grinding it into a powder; and the process of making a paper from such resin, and the paper made by the process, forms a specific object of the invention.

A urea formaldehyde synthetic resin is formed by the reaction of formaldehyde on a carbamide as a urea or a thiourea. The resultant product, known as a condensation product, can exist in three forms or stages and a lower stage can be changed, and will of itself slowly change, into an upper stage.

The first stage of the combination of urea and formaldehyde is liquid. the dispersion mixture being mostly water. If a coat of this liquid is applied to the surface of a glass plate and then dried at room temperature, it will be found that the film of resin which remains on the plate can be washed off with water, indicating that the resin at this stage of the condensation is water soluble. The combination of urea formaldehyde may be made in such a way that the product will remain permanently liquid and of a waterlike transparency.

If heat is applied to the above described solution. or if a small quantity of any one of several kinds of salts, which act as accelerators or catalyzers, is added to the solution, the latter will gradually thicken and will reach, after a lapse of time which varies with the components, the condition of a more or less solid jelly. In this second or jelly stage, the resin is water insoluble but is fusible. If this jelly is left to itself in the open air and particularly if it is exposed to the action of sunlight, it will contract, lose gradually its water content, and will ultimately arrive at a stage, the third stage. where it is hard and infusible. In this condition. if suflicient heat is applied to the resin, it will char and then burn without fusin This transformation of the jelly to the t 1ird and infusible stage will occur much quicker if the jelly is subjected when freshly made to the action of cat.

In carrying out my invention, I use the urea formaldehyde synthetic resin in its second or water insoluble, fusible jelly stage. While I may use a jelly which has been prepared by any satisfactory formula, I prefer to make it by the process disclosed in my copending application Serial No. 309,118, filed September 28, 1928.

In accordance with such process, a urea, accompanied if desired, by a plasticizing agent and an accelerator, is subjected to the action of acetaldehyde in the cold. A reaction takes place which produces an intermediate compound of a colloidal, gelatinous nature, which I have termed A-gum.

A satisfactory formula is Grams Urea 100 Glycerin 50 Acetic acid (glacial) 10 In the above formula, glycerin is the lasticizin agent and acetic acid is the acce erator. Tb this mixture fifty grams of commercially pure acetaldehyde is added. The A- gum is produced from the resultant reaction. This A-gum when cold will be either a thick transparent liquid or a milky rather firm solid according to the pro ortions of the ingredients in the above ormula. I prefer the A-gum as a semi-liquid compound. The A-gum is soluble in water.

The jelly resin is prepared from the A-gum by treating it with formaldehyde preferably in the presence of an accelerator. A suitable formula may be the following, which is given in my above named co-pending application.

Grams A-gum 100 Formaldehyde 150 Ammonium sulphate 2-5 With the above proportions, the jelly resulting from the reaction is opaque and milky white. The jelly at this stage, as has been previously set forth, will gradually change into a hard solid infusible resin.

It has been found that, if it is attempted to introduce the jelly into the beater with the paper making fibres after the jelly has stood for a few days, the paper made from the mixture will be uneven in color and will contain white spots distributed throughout it and an examination of the jelly will bring forth the fact that the jelly contains a large proportion of hard, gritty particles which indicates that a part of the jelly has already become converted into the third and solid infusible state.

If it were commercially practical to mix the jelly immediately after it was made with the paper making fibres in the beater, a satisfactory paper having essentially the characteristics of the paper about to be described could be made. However, it is not commercially feasible to introduce the freshly made jelly into the beater. Consequently, the jelly in the. process of manufacture is treated so as to retard, for a suitably long period, its further condensation or change into its final hard and infusible stage. This particular treatment of the jell and the resultant product, is described an claimed in my co-pending application Serial No. 309,120, filed September 28, 1928. In accordance with the disclosure in this application, the process of making the jelly is modified by the introduction of an agent which will act to retard the development of the third and final stage of the jelly resin. I have found that if the jelly is intimately associated with a colloidal or mucilaginous material as, for instance, tragacanthr gum, karaya gum, India gum and the like, or starch, dextrine and the like, the jelly will be so slow in ageing that it will stay soft and in proper condition for use in the manufacture of my paper for a long time, as more than two months and that, at the end of this period, the jelly upon being crushed beneath the fingers will not give any feeling of containing gritty particles and,

- when the paper is finished and calendered, it

will be impossible to detect on its surface any particle or resin of any size which stands up on the back ground of fibres. The mucilage thus acts as-a retarder for the jelly.

In order to effect an intimate association of the retarder and the jelly resin, I introduce the retarder into the reacting agents prior to the formation of the jelly. To this end, I prepare a retarding solution which can be made as follows:

Parts lVater I00 Karaya gum 2. 5

This retarding solution is introduced into the solution of A-gum, formaldehyde and ammonium sulphate above described before the reaction or condensation has progressed to the jelly stage. Thus, the jelly condensation product contains a suitable proportion of retarder to delay its conversion into the third stage for a suflicient period of time to make the paper making process commercially feasible. If the jelly resin is prepared by the usual process of boiling urea and formaldehyde, the mucilage solution can be added before the boiling is started, or, at least, before the jelly has begun to form.

In carrying out my paper making process, I mix the jelly resin either when freshly made or, for the commercial process, with a retarder associated with it with the paper making fibres in the usual paper beater. The paper making fibres can be any usual or desirable fibres as wood pulp, rag stock, cotton batting and the like, or a mixture thereof. The amount of jelly resin added to the beater may vary within wide limits depending upon the characteristics required of the finished paper sheet. For instance, for each 100 pounds of dry pulp in the beater I can put in a weight of jelly resin varying between 5% and 100% of the weight of the pulp. The weight of jelly resin can even be increased above 100% as this is not even the limit of the amount of jelly resin which the pulp fibres may carry. I find that the jelly resin has a great aflinity for the paper making fibres to the extent that when the heater is emptied not a particle of jelly can be found at the bottom. In the beater, the elly is dispersed throughout the pulp stock and by reason of its great affinity for the fibres is adsorbed thereby and thus is taken up by the surface of the fibres so that when the beating operation is completed there is substantially no free jelly in the water of the beater. The time of beating will be long enough to cause the jelly to be taken up by the paper making fibres. Usually this will be no longer than is required to beat up the fibres themselves. Instead of introducing the jelly mass directly into the beater and depending upon the beating action to break up the jelly, I prefer first to grind the jelly with water and to put the mixture into the beater as I find that a better dispersion of the resin and consequently a better sheet is obtained.

The paper pulp thus prepared is made into a paper sheet in any usual manner as in a F ourdrinier or cylinder machine depending upon the kind of paper that is being made.

The method and apparatus for laying the paper sheet is the same as is usual in the art. The wet paper sheet is then dried in any suitable manner and by any suitable apparatus as the usual presses and drying rolls with the exception that the paper is not heated or is only slightly heated so that the drying takes place at about room temperature, the purpose being to prevent the conversion of the jelly resin of the sheet from the fusible to the solid infusible stage.

The paper is then calendered preferably without the application of heat. Preferably the sheet should have a material amount of moisture in it or be in temper as I find that the presence of some moisture improves the combination between the fibres and the jelly. Preferably the calendering pressure is heavy for making sheets of the greatest mechanical strength, although if, for some purpose, mechanical strength and denseness of paper are not important, the calendering pressure can be lessened, although the calendering pressure ordinarily is substantial.

I find that a marked transformation occurs in the jelly-containing paper as a result of the calendering operation. The paper before the calendering appears like the usual paper. However, after itis passed through the calender rolls, it is found that the paper has become translucent and looks parchmentized. At the same time, it will be found that its tensile strength, as compared with that of other papers of the same weight, is increased. Its resistance to the action of chemical agents and also its electrical resistance is found to have been increased over that of ordinary calendered papers. The translucent and parchmentized appearance of the calendered paper undoubtedly results from the great afiinity between the jelly resin and the cellulosic fibres of the paper so that, under the calendering pressure, it is caused to have a much greater degree of s read between the fibres and to have a mile greater degree of binding with the fibres than is the action of an ordinary rosin sizing. The calendering pressure appears to force the resin into the voids between the fibres and to compact the resin particles into an integral film which permeates the paper sheet and adheres strongly to and binds the fibres firmly together.

If the thickness of the paper is increased to the thickness of cardboard, the translucency as to be expected diminishes correspondingly. The sheet as itis increased in thickness becomes eventually opaque but preserves nevertheless its extraordinary toughness and parchmentized appearance. In this condition the material may be compared with the highest and most expensive grade of parchmentized fibre board.

I have found that the toughness and especially the translucency of my paper are rather improved if to the beater is added a moderate amount of rosin sizing as, for example, from three to five per cent of the weight of the pulp, followed by the proper amount of alum. Other sizings can also be used advantageously as for instance an emulsion of rosin and parafiin in suitable amounts.

The paper prepared in accordance with nay above described method has many of the a vantages of a parchmentized sheet and the speedy process of manufacture of my sheet is a marked improvement over the slow and complicated process of manufacturing parchmentized papers.

For some purposes it may be desirable to have the jelly resin in the paper in its last or infusible form. This can be done by heating the calendered paper to a suitably high temperature for a sufiieient period of time to carry out the final condensation of the resin. hen the resin has been converted to the hard infusible form its flexibility will have been reduced.

The glycerin which is present in the manufacture of the A-gum is also present in the resin and adds flexibility to the finished sheet.

The glycerin can be replaced by an ester thereof as acetin, for instance, or omitted.

I claim:

1. The process of making paper which consists in disintegrating a urea formaldehyde resin in the water insoluble jelly stage in a paper beater with paper making fibres, beating the mixture until the jelly resin has been taken up by the fibres, and forming a paper sheet from such fibres.

The process of making paper which consists in disintegrating a urea formaldehyde resin in the water insoluble jelly stage in a paper beater with paper making fibres, beating the mixture until the jelly resin has been taken up by the fibres, forming a paper sheet from such fibres, removing water from the sheet, and heavily calendering the sheet.

3. The process of making paper which consists in mixing paper stock and a water insoluble jelly of a urea formaldehyde resin, forming a paper sheet of the mixture, drying the paper at a sufficiently low temperature to maintain the jelly resin as such, and calendering the sheet. a

4. The process of making paper which consists in mixing paper stock and urea formaldehyde resin in the water-insoluble fusible jelly stage, forming a paper sheet from such mixture, partly drying the sheet, stopping the drying process while the sheet yet contains a substantial amount of moisture, and calender-ing the partly dried sheet.

5. The process of making a resin-containing paper which consists in mixing paper 100 making fibres and a urea formaldehyde resin in the water insoluble fusible jelly stage, which resin contains a retarder, forming a paper sheet of such mixture, and drying and calender-ing the sheet.

6. The process of making a resin-containing paper which consists in mixing paper making fibres and a. urea formaldehyde resin in the water insoluble jelly stage, which resin contains a retarder, forming a paper sheet of 110 such mixture, and drying the sheet at such a low temperature that the jelly resin remains in a fusible stage, and calendering the sheet.

7. The process of making a resin-containing paper which consists in mixing paper 11 making fibres and a urea formaldehyde resin in the water insoluble fusible jelly stage, which resin contains a retarder, forming a paper sheet of such mixture, drying the sheet at such a low temperature that the jelly resin 120 remains in a fusible stage, stopping the drying process while the paper yet contains a substantial amount of moisture, and calenderin g the sheet.

8. The process as defined in claim 5 where- 1 in the retarder comprises a colloidal substance.

9. The process as defined in claim 5 wherein the retarder comprises a mucilage.

10. The process as defined in claim 5 in wherein the retarder comprises karaya gum.

11. The process of making a resin-containing paper which consists in mixing paper stock and a synthetic resin in a water insoluble fusible jelly form, forming a sheet of said mixture, and drying and calendering the sheet;

12. The process of making a resin-containing paper which consists in mixing paper stock and a synthetic resin in a water insoluble fusible jelly form associated with a retarder, forming a paper sheet of such mixture and drying and calendering the sheet.

' 13. The process as defined in claim 12 wherein the retarder comprises a mucilaginous material.

14. The process of making paper which consists with mixing with paper making fibres a water insoluble synthetic resin: jelly which has a marked affinity for the fibres and is adsorbed by the fibres, and forming a paper sheet of said jelly-adsorbed fibres.

15. The process of making a resin-containing paper which consists in mixing paper stock with a resinous condensation product that is in its intermediate water-insoluble and fusible jelly stage, forming a paper sheet from such mixture, drying the sheet at a sufficiently low temperature to maintain the resin in its intermediate stage, and calendering the sheet under sufiicient pressure to spread the resin throughout the sheet and to bind the fibres together.

16. The process of making a resin-containing paper which consists in mixing paper stock with a resinous condensation product that is in its intermediate water-insoluble and fusible jelly stage, forming a paper sheet I synthetic resin in the water insoluble fusible jelly form and a small amount of a sizing containing rosin. forming a paper sheet from such mixture and drying and calendering the sheet.

18. The process of making paper which consists in mixing together paper making stock, water-insoluble jelly, and a small amount of a. sizing, forming a paper sheet from such mixture, and drying and calendering the sheet.

19. The process of making a resin-containing paper which consists in mixing a resinous condensation product which is in an intermediate jelly stage of condensation with paper stock, forming a sheet of such mixture, at least partly drying the sheet, and calendering the sheet under sufficient pressure to spread the resinous condensation product as I a film throughout the sheet.

20. The process of making a resin-containing paper which consists in mixing a synthetic resin as a jelly containing a plasticizing material with the paper making stock, forming a paper from the mixture, removing water from the paper, and applying a pressure to the paper.

21. A paper sheet composed of paper making fibres and a urea formaldehyde synthetic resin which has been distributed throughout the sheet and on and amongst the fibres in its water insoluble fusible elly form;

22. A paper sheet containing on and betweenits fibres a urea formaldehyde resin in an intermediate stage of condensation, and a retarder which retards the progress of condensation of the resin.

23. A paper sheet containing paper making fibres which are bound together by a resinous condensation product which has been incorporated in the paper pulp while the resin is in a water insoluble fusible jelly stage.

l4. Paper consisting of an intimately compacted and bonded mixture of paper stock and a urea formaldehyde condensation product, which has been incorporated in its jelly stage with the paper stock.

25. Paper consisting of an intimately compacted and bonded mixture of paper stock and a urea formaldehyde condensation product in a water-insoluble fusible stage, which product contains a retarder to hinder further condensation of said condensation product.

26. Paper consisting of an intimately compacted and bonded mixture of paper stock and a urea formaldehyde condensation product which has been incorporated in its jelly stage with the paper stock, said condensation product being present as a film which envelopes and occupies the Voids between and is strongly adherent to the paper making fibres.

27. A paper sheet containing paper making fibres pressure-bonded together by a urea formaldehyde resin which contains a plasticizing agent that imparts flexibility to the sheet.

28. In the process of making paper the steps of mixing a urea formaldehyde jelly resin to the paper stock and then forming a paper sheet from such mixture.

29. A paper sheet formed by the mixing of a urea formaldehyde jelly resin with the paper making stock prior to the formation of the paper sheet.

30. The process of making paper which consists in forming a paper sheet from paper stock containing a water-insoluble jelly.

31. The process of making paper which consists in forming a paper sheet from paper stock containing a urea formaldehyde resin in a water-insoluble jelly form.

32. The rocess of making paper which consists in orming a paper sheet from paper stock containing a urea formaldehyde resin in a water-insoluble jelly form, and a retarder for the resin.

33. The process of making paper which consists in forming a paper sheet from paper stock containing a water-insoluble jelly, and calendering the sheet under sufficiently heavy pressure to spread the jelly through out the sheet and into the voids between the fibres.

34. The process of making paper which consists in mixing water-insoluble jelly with paper making fibres until the jelly has been taken up by the fibres, and forming a paper sheet from such fibres.

35. The process of making paper which consists in mixing a disintegrated water-insoluble jelly with paper stock and forming a sheet from such mixture.

In testimony whereof, I have signed my name to this specification.

ERNEST LIONNE. 

